Morrison won the FA Youth Cup with United in 2011, scoring two goals in the final, but his time at the club was blighted by behavioural issues including several brushes with the law.

He was cautioned for common assault in 2008, and pleaded guilty to witness intimidation in February 2011. Three months later, he was fined £600 for throwing his girlfriend's phone through an open window during a row.

"He needed to get out of Manchester," Phelan told BBC Radio 5 live. "He has gone away from the club now which I think, in hindsight, is the correct thing to have done.

"It is easy to say we let our most promising player leave, but is it worth the hassle to wait and maybe not see fruition to it?"

After a loan move to Championship side Birmingham last season, he has netted four goals in eight games for the Londoners this time, prompting Allardyce to say that "the penny has dropped".

And Phelan, who left United after Ferguson retired at the end of last season, hopes the player does not suffer any more setbacks.

"It is still a risk with Ravel, but he seems to have got his head in the right situation -- his performances are decent and getting better. Hopefully he can maintain that," Phelan added.

"At Manchester United there were other things going on which were a distraction for him, and that played a part in his downfall. He had a tendency to disappear for the odd day or two and then we would manage to find him and bring him back in.

"It really was a day-to-day project with him. One day he was there and then another he wasn't. He is a nice guy when he is with you, when he is around football, but obviously there were distractions.

"At the end of the day, is it too much work to put into one person and keep the harmony and the balance? That was a decision that the club had to make."